Structure of FPC
According to the number of layers of conductive copper foil, FPC
can be divided into single layer circuit, double layer circuit,
multi-layer circuit, double sided and so on.
Single-layer structure: the flexible circuit of this structure is
the simplest structure of the flexible PCB. Usually the base
material (dielectric substrates) + transparent rubber(adhesive) +
copper foil is a set of purchased raw materials(semi-manufactures),
the protective film and transparent glue are another kind of bought
raw material. First, copper foil must be etched to obtain the
required circuit, and the protective film should be drilled to
reveal the corresponding pad. After cleaning, the two are combined
by rolling. Then the exposed part of the pad electroplated gold or
tin to protect. In this way, the big panel board will be ready.
Generally also it’s stamped into the corresponding shape of the
small circuit board. There is also no protective film directly on
the copper foil, but printed resistance soldering coating, so that
the cost will be lower, but the mechanical strength of the circuit
board will become worse. Unless the strength requirement is not
high and the price needs to be as low as possible, it is best to
apply the protective film method.
Double layer structure: when the circuit is too complex to be
wired, or copper foil is needed to shield the ground, it is
necessary to choose a double layer or even a multilayer. The most
typical difference between a multilayer and a single plate is the
addition of a perforated structure to connect the layers of copper
foil. The first process of transparent rubber + base material +
copper foil is to make holes. Drill holes in the base material and
copper foil first, clean and then plated with a certain thickness
of copper. The subsequent fabrication process is almost the same as
the single-layer circuit.
Double sided structure: both sides of the double sided FPC have
pads, mainly used to connect other circuit boards. Although it and
monolayer structure is similar, but the manufacturing process is
very different. Its raw material is copper foil, protective film
and transparent glue. The protective film should be drilled
according to the position of the pad first, then the copper foil
should be affixed, the pad and track lines should be etched and
then the protective film of another drilled hole should be affixed.
FPC Case: Multilayer 4 Layer Flexible PCB for GPRS Router
(Flexible printed circuits are custom-made products, the picture
and parameters shown are just for reference)
General description
This is a type of flexible printed circuit for the application of
GPRS Router. It’s a 4 layer multilayer FPC at 0.25mm thick. The
base laminate is from ITEQ, It’s fabricated per IPC 6012 Class 2
using supplied Gerber data.
Parameter and data sheet
| Size of Flexible PCB | 50.32 X 30.28mm |
| Number of Layers | 4 |
| Board Type | Flexible PCB |
| Board Thickness | 0.25mm |
| Board Material | Polyimide 25µm |
| Board Material Supplier | ITEQ |
| Tg Value of Board Material | 60℃ |
|
| PTH Cu thickness | ≥20 µm |
| Inner Iayer Cu thicknes | 35 µm |
| Surface Cu thickness | 35 µm |
| |
| Coverlay Colour | Yellow / Black |
| Number of Coverlay | 2 |
| Thickness of Coverlay | 25 µm |
| Stiffener Material | no |
| Stiffener Thickness | N/A |
| |
| Type of Silkscreen Ink | IJR-4000 MW300 |
| Supplier of Silkscreen | TAIYO |
| Color of Silkscreen | White |
| Number of Silkscreen | 1 |
|
| Peeling test of Coverlay | No peelable |
| Legend Adhesion | 3M 90℃ No peeling after Min. 3 times test |
|
| Surface Finish | Immersion Gold |
| Thickness of Nickle/Gold | Au: 0.03µm(Min.); Ni 2-4µm |
| RoHS Required | Yes |
| Famability | 94-V0 |
|
| Thermal Shock Test | Pass, -25℃±125℃, 1000 cycles. |
| Thermal Stress | Pass, 300±5℃,10 seconds, 3 cycles. No delamination, no blistering. |
| Function | 100% Pass electrical test |
| Workmanship | Compliance with IPC-A-600H & IPC-6013C Class 2 |
Features and benefits
Excellent flexibility
Reducing the volume
Weight reduction
Consistency of assembly
Increased reliability
Controllability of electrical parameter design
The end can be whole soldered
Material optionality
Low cost
Continuity of processing
Great customer service
Delivery on time: >98%
Application
Flexible flat cable, medical equipment controller, consumer card
reader soft board
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